Our spectrometer is uniquely equipped for applications to a wide range of disciplines, including catalysis, geochemistry, materials synthesis and characterization, and membrane research activities.
Catalysis
Catalytic reactions often involve complex processes spanning multiple phases. Take, for example, the hydrogenolysis of lignin, a crucial step in sustainable biomass conversion. This reaction necessitates samples encompassing solid, liquid, and gas phases, including liquid solvents, metal-doped catalysts supported on activated carbon or metal oxides, and high-pressure H2 gas exceeding 35 bar. Operating at temperatures above 150°C, our specialized high-temperature and high-pressure spectrometer offers a unique capability: simultaneous characterization of analytes dissolved in the solvent, insoluble analytes and condensation products, and adsorbed analytes onto catalyst surfaces.
Similarly, the conversion of cellulose to glucose, and further to fructose and 5-hydroxymethylfurfural (HMF), presents another challenging reaction to monitor. Using a ZrP catalyst in water at 150°C, our spectrometer enables real-time tracking of this transformation. Employing an alternating cross-polarization (CP) and direct polarization (DP) with low proton decoupling experiment, we observe analytes both in the solid state (via CP) and in solution (via low-decoupling DP) as the reaction progresses. Over time, resonances associated with cellulose decrease while signals corresponding to glucose, fructose, and HMF increase, providing invaluable insights into reaction kinetics and product formation.
Geochemistry
Utilizing Nuclear Magnetic Resonance (NMR) with Magic Angle Spinning (MAS), our facility offers a powerful tool for analyzing liquid-solid biphasic geochemical reactions. This advanced technique provides unparalleled element-specificity, sensitivity to both light and heavy elements, and access to comprehensive structural and dynamic information. Moreover, NMR enables the analysis of heterogeneous mixtures encompassing dissolved, precipitated, and brine-soaked minerals.
With our high temperature and pressure capability, we extend the scope of NMR analysis to liquid-solid biphasic reactions occurring under supercritical fluid conditions. Such conditions are highly relevant to geochemical processes like CO2 sequestration. By subjecting samples to elevated temperatures and pressures, we can delve into the intricacies of geochemical reactions taking place in these extreme environments, providing invaluable insights into fundamental mechanisms and reaction kinetics.
Our facility empowers researchers to unravel the complexities of geochemical systems with unprecedented precision, shedding light on processes crucial for understanding environmental phenomena and geological transformations.
Materials Science
Traditional studies of material phase transformation or degradation kinetics and mechanisms are typically carried out ex-situ, where materials are collected from synthesis or degradation mixtures before being characterized for molecular, morphological, and/or phase structure. However, this approach may not capture the dynamic processes occurring during synthesis or degradation, leading to uncertainties regarding the true molecular and structural evolution of the materials.
As an example, as described by Cunniff et al. in a study conducted at Pacific Northwest National Laboratories, several strategies for mitigating the accumulation of carbon dioxide in the atmosphere involves bringing supercritical CO2 in contact with phyllosilicates. By employing in-situ nuclear magnetic resonance (NMR) techniques with high temperature and pressure capabilities, they were able to study the scCO2 adsorption properties of PB2+, RB+, and NH4+ smectite clays at various relative humidities.
2022 38 (50), 15540-15551. DOI: 10.1021/acs.langmuir.2c02139
Another application is for the synthesis of mechanically interlocked molecules, which often requires templation under elevated pressure and temperature conditions. Understanding the effect of pressure on the orthogonal metal-templated synthesis of MIMs and investigating the interactions between functional groups is crucial for optimizing the synthesis process and improving the yield of desired MIMs. In-situ NMR can be used to analyze the structural changes occurring in the precursor molecules and intermediates during the templation process, providing valuable mechanistic insights into the formation of MIMs.
Membranes
In-situ or operando characterization of materials in membranes under operational temperatures and pressures is crucial for gaining insights into the relationships between membrane structure and transport behavior. By employing high-temperature and high-pressure NMR techniques, researchers can directly observe and analyze the molecular dynamics and structural changes occurring within membranes during operation. This real-time monitoring provides valuable information for developing materials tailored to specific applications, optimizing membrane synthesis processes, and enhancing membrane quality and stability.
For example, Walter et al. at Pacific Northwest National Laboratories used solid-state NMR in combination with solution NMR and computational techniques to help characterize interactions between CO2 and (polyether ether ketone)-ionene membranes. Similarly, in the development of proton exchange membranes for fuel cells, in-situ NMR enables the characterization of proton transport pathways and interactions within the membrane structure, aiding in the design of more efficient proton conductors.
Furthermore, in-situ NMR characterization can help identify performance-limiting factors in membranes, allowing researchers to address key challenges and refine membrane fabrication methods. By understanding the complex interplay between membrane composition, structure, and function under realistic operating conditions, scientists can accelerate the development of advanced membrane materials with tailored properties for diverse applications, including water purification, gas separation, and energy conversion.